I just bought the 6164 about a month ago and a first I thought the picture quality was crappy but then i realized I needed glasses.
So after i got glasses I realized that the best viewing angle for this TV is dead on center and low. If you are higher then the TV it will be less brighter and less clearer, if you are on the side, same thing. I veiw it from upto 20 ft with my glasses and I see a clear picture.
Also you have to relize what kinda a picture. Regular cable (not digital) cable, gives me a snowy, blurry picture. Some channels are better then others, global, CTV, CFMT are very clear (Rogers Cable Toronto Canada). I then have my satellite receiver hooked up to my TV via S-Video. This is an improvement over regular cable. PPV channels are by far clearest, sharpest pictures. Then I have HDMI DVD player Samsung. The picture quality is superb, especially widescreen enhanced DVD's. Gladiator, Lord of the Rings, Peral Harbour give fantastic colour and clarity. I was watching the sopranos, and I noticed that the whites where super white. The rest was clear picture, but the white were somehow live and snowy, I then realized the the DVD player has a brightness setting and it was set on 5 (max) i lowered this setting to 2 and the white phenomeon went away. I also noticed that the 720p is a bit better then 1080i but I know this varies with whether or not the DVD is widescreen enhanced or not.
Overall, after i got glasses, I realized this 6164 is incredible for a widescreen. The only thing I dont like is the remote. IT has a joystick, very cheap feeling. I think I have the wrong remote because what I have is different from whats in the manual. The manual shows a remote without a joystick.
I;ve had it for a month I clocked 250 hours so far on this DLP.
As for my settings, I used cinema mode with contrast and sharpness in the high 80's, and brightness in the high 50's and colour I think at 50.